This project studies congenital heart disease on a city wide basis. Hearts from the city of Chicago are funnelled through the center where they are diagnosed and reports sent to each individual hospital. This forms the basis of research on masses of hearts, especially from the standpoint as to what is important to the surgeon. In addition, the conduction system is studied in congenitally abnormal hearts and hearts from patients with arrhythmia, and sudden death. Correlation is made with His bundle recordings and electrocardiography.